1. Field of the Invention
The present invention relates to thread feed mechanism and a method for feeding weft threads, catch threads or the like in textile machines.
2. Prior Art
For feeding yarn or thread in a textile machine, frequently the yarn or thread is looped one or more times around a driven feed roller and tensioned to prevent slippage. In machines where the feed roller is driven at a constant speed, the speed at which the thread is fed is determined by the circumference of the roller.
"Expandable" feed rollers are known in which side-by-side discs normally fixed to a driven drive shaft have respective inclined, interdigitated fins or fingers forming a valley of alternating inclined fins in which the loop or loops of thread ride. The relative positions of the two discs determine the circumference of the base of the valley and, consequently, the thread feed rate. With the textile machine and the feed roller drive shaft stopped, the mechanism fixing the discs on the drive shaft can be disengaged so that the dics can be moved axially toward or away from each other to change their relative axial positions and, hence, the circumference of the base of the thread-receiving valley formed between them. Spacers of various sizes are used to assure a reasonably precise adjustment from a reference position. By adding or removing spacers, the relative positions of the feed roller discs can be changed in desired increments.
Stopping the textile machine to allow adjustment of the thread feed rate results in loss of production. In addition, experience has shown that the correct spacing of the discs can be determined only after one or more test runs, so that usually more than one adjusting operation is required.